Heat cushions or hot water bottles are traditionally made from a thick rubber material constituting a chamber and with an outwardly protruding feeding nozzle so that heated water may be poured into the chamber. After filling in water, the feeding nozzle can be sealed, for instance by means of a screw plug. Such a similar heat cushion is e.g. known from GB 2.290.705 relating to a cushion for the back of the head which may be filled with a heating fluid through a neck. The neck is adapted to receive a sealing body so that the liquid does not run out of the cushion. Said sealing body may for instance be inserted by a screw threat. In an alternative embodiment the liquid is permanently located in the cushion for the back of the head which may be heated in a microwave oven.
U.S. Pat. No. 4,743,726 describes a heating element which can be heated by means of microwaves. The heating element has a flexible cellular core which can absorb water so that the whole core is saturated by water and subsequently can be heated by microwaves. The core is encased in a heat and flame resistant rubber element, which can also be heated by microwaves. This rubber element ensures that the element can be heated to an even higher temperature.
U.S. Pat. No. 5,447,531 relates to a therapeutic heat cushion which is filled with a water-absorbing material containing polyacrylamide. The cushion has an outer layer of material which is water permeable, whereby the cushion can be lowered into water so that the water absorbing material takes up water. Subsequently the cushion can be heated in a microwave oven. The cushion can be dried after use and can be applied several times.
WO/0178797 describes a therapeutic heat cushion the interior of which contains pearls of alumina together with a compound of glycerol and absorbed water. This is sheathed by a cloth with two functionally different surfaces. Thus one side of the cushion is water permeable while the other side is impermeable. Hereby, after heating in a microwave oven, the cushion may be applied either to transfer humid heat or to transfer dry heat.
GB 2.395.910 relates to a heat cushion containing wheat, barley, rice, grain or foam which may be heated in a microwave oven. The cushion has an area adapted to change colour depending on the temperature variations.
U.S. Pat. No. 5,135,518 describes a compress for humid heat treatment. The compress has a water absorbing layer between a liquid impermeable layer and a liquid permeable layer.
Traditional heat cushions which can be filled with heated water have the disadvantage that the pouch may be very “lively” and have a tendency to gather water when the cushion is applied as a heat compress, not achieving a uniform heat supply at the respective place on the body where the compress is used. Furthermore such heat cushions have a tendency to be voluminous. This is also the case for those heat cushions which, via a permanent aqueous core or a grain core are suitable for heating in a microwave oven. Heat cushions having a water absorbing core which are filled by lowering the cushion into water have the disadvantage that they are unhygienic on multiple appliances, as they may gather bacteria in the core, or they may gather several waste products from the human body. Furthermore there is the risk of almost boiling water running out of the cushion and scalding the user.